The decision by Conservative MPs and activists not to change the leadership rules means this week's Conservative party conference becomes of paramount importance in the leadership race. Make no mistake, every candidate will be wearing a bathing suit: this will be a beauty parade.

I'm told that this year's conference will be the most exciting since 1963. As I wasn't there, and this one has not happened yet, I cannot comment. But every candidate will be in full courting mode - and they will be courting not just the 190-odd MPs, but chairmen, councillors and activists from many associations.

I declared early in the contest for David Cameron. As his campaign launch showed, it is possible for a candidate to give his campaign significant momentum with just one event. I was not there and had nothing to do with it, as I was on holiday at the time, but the press reaction has been incredibly positive, and David's campaign has been given a significant boost.

The strategy for conference is obvious: to maintain that momentum. All the candidates will appear at various fringe meetings, which will be well attended by MPs and activists genuinely wishing to size up the contenders.

David is being interviewed by Andrew Rawnsley in a fringe event sponsored by the Observer, and that will be one of the key moments of the conference for him. Like all the other candidates, he will also hold a reception and spend time in the bars and at other receptions talking to activists.

Each candidate's campaign team will also be out and about gathering intelligence and seeking to cajole and persuade neutrals and waverers.

And then, of course, there will be the conference speech.

The conference speech has to be the most important aspect of the four days of conference: each candidate has a unique opportunity to be prime ministerial - or at least "leadershiperial" - in front of a live conference audience and the wider media. Think how important these kind of speeches have been in the past, for both those at the top and at the bottom of the greasy pole.

Hailsham blew it in 1963. Edwina Currie and William Hague marked themselves out as rising stars. Heseltine marked himself as leader in waiting. Thatcher defined herself as the lady who was not for turning.

You can be sure that each candidate will be taking their speech as seriously as possible. They will have to achieve an interesting trick: speaking to their brief but also painting a broader canvas.

Again, as I am not involved in the detail, I can speculate. As his launch showed, David Cameron excels when he speaks without notes, informally, off the cuff. I would expect him to speak as directly as possible to his audience, to show them his energy and enthusiasm for the job but also to personify his own message: that in order to win we have to change. And David personifies the sort of change we need.

All the serious candidates now have a full campaign team in place of strategists, press officers and researchers. So for the media there will be at least four or five simultaneous conferences as each campaign team seeks to "spin" their successes at conference.

In many ways this resembles an American political conference. At last year's Republican convention, I was struck by how many potential candidates were running their own campaigns, whether it was the McCain gig or "cigars with Giuliani". It won't be quite as slick in Blackpool, but you get the gist.

It will be fascinating to see how the media judge the mood, and whom they see emerging as the frontrunners. As on all sporting occasions, there are clear favourites and also-rans; and as on all sporting occasions, there can be upsets.

Conference is, in effect, the first heat of the contest. It will be interesting to see how the candidates rank at the end: it won't necessarily be in the order in which they started.